Textile drafting mechanism



March 11, 1952 SHAW 2,588,420

TEXTILE DRAFTING MECHANISM Filed Aug. 18, 1948 5 Sheets-Sheet 2 March 11, B. C. SHAW TEXTILE DRAFTING MECHANISM Filed Aug. 18, 1948 3 Sheets-Sheet 3 R B 5 12 5 V Patented Mar. 11, 1952 UNITED STATES PATENT OFFICE 2,588,420 reams ISRAFTING MECHANISM Benjamin 0. Shaw, Biddeford; Maine, assignor to Saco-Lowell Shops, Boston, Mass; a. corporation of Maine A pueauon Au ust 1a, 1948, serial No. 44,907

14 Claims; 1

This invention relates to mechanisms for drafting textile fibers, such as cotton, rayon, wool, and others, and mixtures of such fibers, in various stages of the manufacture of spun yarn.

In my Patent No. 2,233,963, dated March 4-, 1941, I have shown and described a drafting mechanism which has proved especially satisfactory in roving and spinning machines for the manufacture of yarns spun from cotton and rayon, the fibers of which are not much longer than those encountered in cotton. My Patent No. 2,329,655, granted September 14, 1943, discloses certain improvements in said mechanism. In both of these inventions I used the principle,

novel in the earlier patent, of a top roll running I in a depressed curve in an apron to control the short fibers. This principle has been widely used commercially in mechanisms which now form the largest part of the production of roving and spinning machines manufactured by the assignee of these inventions.

The present invention is a further development of those disclosed in my earlier patents above designated. In general it aims to greatly extend the range of fiber length which can be successfully handled by these prior mechanisms, and also to afford a better control over all the fibers while they are being drafted, and to reduce the adjustments necessary when changing from one type of fiber, or length of staple, to another.

In the mechanisms shown in my patents above mentioned, the sliver or roving being drafted is gripped firmly between the bite of a pair of upper and lower back rolls, again gripped firmly between a middle top roll and a belt or apron on which it bears and, finally, gripped firmly between the bite of the front rolls or delivery rolls. The peripheral speed of the apron and the middle roll is made in the order of perhaps 1.10 to 1.25, for example, times that of the back rolls so as to produce a pretension or strength in the sliver being drafted. In order better to control the fibers between the middle and front rolls, where the main draft is applied, the middle top roll is arranged to bear on a portion of a belt or apron, stretched between the middle bottom roll and a guide in such a manner as to depress the belt between these points of support so that it will be partially wrapped around the surface of said middle top roll for an angular distance of at least 30. The control so afforded has proved to be very valuable. In these mechanisms, when running cotton, which naturally contains many short fibers together with longer ones, good drafting requires that the distance between the positive bite at the front rolls and the positive bite between the middle top roll and the apron be made greater than the length of the majority of the fibers. The shorter fibers are controlled by the yielding grip exerted on them by the apron and that portion of the surface of the middle top roll running closely adjacent to the apron as they leave the point of positive grip between these elements and approach the front rolls.

In experimenting with these mechanisms I proved that if the positive grip between the middle top roll and the apron was reduced and made a relatively soft yielding grip, I obtained a far better control over all the fibers and realized a flexibility or tolerance in handling wide variations in staple length that was truly astonishing. This was all the more so because the pretension or stretch; as we have known it, disappeared and the drafting no longer was accomplished in two distinct tones but took place in a single zone limited only by the spacing of the front rolls from the rear rolls. 7

The present invention is based primarily on the development of the idea discovered in the manner just described.

The nature of this invention will be readily understood from the following description when read in connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims.

In the drawings,

Fig. 1 is a plan view of a short section of a drafting mechanism constructed in accordance with this invention and adapted for use in a spinning or roving frame; M

Fig. 2 is a front elevation of the mechanism shown in Fig. 1;

Fig. 3 is a transverse, vertical section of the mechanism illustrated in Fig. i;

Fig. 4 is a diagrammatic view illustrating a typical setting of the drafting rolls and shows some details of the control mechanism;

Fig. 4a is a diagrammatic view similar to Fig. 4 but modified in that the middle top roll is geared directly to the middle bottom roll so that its drive is positive;

Fig. 5 is a sectional elevation showing part of the means for supporting the middle top roll;

Fig; 6 is a diagrammatic view illustrating the path which the sliver takes in passing through the drawing and control mechanisms and illustrates, on a larger scale, the relation of the elements of the control mechanism to each other;

and

Fig. 7 is a longitudinal, sectional view on the line 1-1, Fig. 4.

Preliminary to a detailed description of the construction shown in the drawings, it may be pointed out that the method provided by this invention comprises the steps of feeding a sliver or roving through a drafting zone having feeding and drafting elements at opposite ends of it which exert a firm bite on the sliver, and controlling the drafting operation at a point spaced from, but closely adjacent to, the delivery end of the zone by guiding the sliver between relatively yielding elements which travel in the same direction as the sliver and at a speed only slightly greater than that at which the sliver is fed into the drafting zone. Such control is attained by causing the relatively yielding surfaces of large area, between which the sliver is gripped as it passes through the control device, to apply only sufficient pressure or resistance to restrict and govern the freedom of movement of the fibers of which the sliver is composed but, nevertheless, so limiting that pressure or resistance that as the forward ends of individual fibers are positively gripped; in the bite of the drafting elements at the delivery end of the zone, they can be pulled through the control mechanism and the body of fibers yieldingly held at any instant in said control mechanism. The construction shown in the drawings is organized and arranged to perform this process.

Referring first to Figs. 1, 2 and 3, the machine there shown comprises front, middle and, rear bottom rolls 2, 3 and 4, top rolls 5, 6 and 7 cooperating, respectively, with them, a belt or apron 8 running over the middle lower roll 3 and the guide bar 9, and a tensioning roll IQ for this apron, the latter being controlled by the usual guide II pivoted on the horizontal bar I2. So far as this arrangement broadly is concerned, it is similar to those shown in my earlier patents and widely used in spinning and roving frames. The three bottom rolls 2, 3 and 4 are driven in the customary manner by gearing located at the end of the spinning or roving frame.

The arrangement here illustrated, however, differs from those used heretofore in that the front and middle bottom rolls 2 and 3 are supported'in fixed relationship to each other, the former in bearings formed in the roll stand l3 and the latter in bearing blocks 14 secured in a fixed position on the roll stand bar or arm l3, Fig. 3. Supporting the rear bottom roll 4 is a bearing block l which is mounted for longitudinal adjustment on the bar [3 toward and from the middle roll, and it is secured in its adjusted} position by the bolt I6. The sections of the apron bar may be supported approximately end to end in the customary manner in slots formed in the roll stand or in the bearing blocks l4.

The front and rear top rolls 5 and I are each provided with two bosses, as is customary; and

they have gudgeons at their opposite ends .which Cooperating with the front and rear top rolls is a weighting mechanism comprising front and. rear weight hooks 22 and 23, the lower ends of which are pivoted to the opposite ends of a rocker or spreader bar 24, Fig. 3. A link 25, pivoted to the central portion of this rocker bar, is provided at its lower end with a hook which releasably engages a pin 23 secured in the flanges of a channel-shaped lever 21 fulcrumed at 28 on the roll beam 30. A plunger 3i is forced upwardly by a spring 32 against said lever and operates through the connections just described to weight both top rolls 5 and l. The middle top roll 6 is independently weighted by a spring hook 33, Fig. 3, pivoted on a small bracket 34 which is secured rigidly to the apron bar 9.

As above stated, the overall draft is produced by the difference in speed of the delivery rolls 2 and 5 as compared to that of the holding rolls 4 and I. In order to maintain a firm bite on the sliver at both of these pairs of rolls, the lower rolls preferably are finely flutedand machined accurately, and the upper rolls are covered with an elastic material, such as synthetic rubber, of sufficient firmness to cooperate with the lower rolls to produce a dependable bite but still having sufficient softness and elasticity to conform to variations in cross-sectional shape of the sliver being fed between them. A synthetic rubber compound made from a neoprene base and of a durometer hardness of in the neighborhood of 50 to '75, answers this purpose very satisfactorily. More weight than that customarily used in drafting cotton should be applied to the top rolls'5 and 1 to preventany slip between the sliver and the rolls. The front top roll 5 especially should be heavily weighted.

The heart of this invention is the control mechanism and its relation to the other elements of the machine. As best shown in Figs. 3 and 6 it comprises the middle top roll 6, the apron B, and the support for said apron afforded by the apron bar 9 and the middle bottom roll 3 which also drives the apron. These two lastmentioned parts support the apron. Preferably, the top roll 5 is pressed against that portion of the apron between the lower middle roll 3 and the apron bar 9 sufficiently hard to produce a sag or curve in the apron and the roving while they move through this area, as in my patents above mentioned. However, the movement of the top roll 6 toward the parts 3 and 9 is definitely limited by the fact that the metal body portion of the roll 6 is cut away to receive the resilient body R, Fig. '7, but the metal roll parts at the opposite ends R of this body are made at least as large in diameter, and often from ten to fifteen thousandths of an inch larger than the elastic section. These solid ends of the roll bear on the apron and, in the preferred form of my apparatus, perform three functions, as follows:

1. To drive the middle top roll 6 at approximately the same surface speed as the apron;

2. To limit the approach of said elastic body of the roll to the apron and to its driving roll 3; and

3. By pressing the belt 8 against the middle bottom roll 3 to improve the driving relationship of the latter roll to the apron and also that of the apron to the top roll 6. r

If the elastic body R is made smaller in diameter than the ends R, then a clearance of predetermined degree is maintained between the fiber contacting surface of this middle top roll and the apron. Such clearance is highly useful in limiting the degree of pressure with which this roll and the apron grip the sliver as the latter travels through the control mechanism. Because the roll ends take the weight applied to the roll, its middle cushion section, in effect, is unweighted except when it bears on a sliver.- Moreover, the body R should be made of a soft, elastic composition, such as rubber, either natural or synthetic, (the latter being prefer-red) so that the pressure with which the sliver is held between this rubber body and the apron is a soft, yielding or cushioned grip. For this purpose the rubber composition should have a very low Shore durometer reading, say from 15 to 25, or thereabouts. It will be understood, however, that the degree of grip required may vary with the nature of the fibers of which the sliver is composed and with the size of the sliver and the yarn to be spun from it. In exceptional cases, especially if the apron is thick and has a good degree of resilience, a clearance alone (i. e. with no rubber cushion) of, say, ten thousandths of an inch, or thereabouts, between the metal surface of the roll and the apron is sufiicient for some, of the purposes of this invention.

The degree and quality of this cushioning grip desired for the purposes of this invention may be further increased and predetermined by cutting a circumferential groove in the lower roll 3, narrower than the width of the apron, and preferably about the axial length of the cushion R in the upper roll. Such grooves are shown at C in Fig. 7. They provide spaces in the lower roll into which each apron can be yieldingly depressed by the sliver or roving as it is fed between each top roll and its respective apron. In

other words, the cushioning effect desired can be produced in either the top roll or the bottom roll, or they can be combined to afford a maximum of yield or softness, as desired.

A definite minimum clearance of about onesixteenth of an inch also is maintained between the ends of the roll 5 and the top of the apron bar 9. thirty-second of an inch in thickness, this provides a clearance, radially opposite the aproncontacting ends of the roll and before where the apron is drawn over the nose of the apron bar, of about one thirty-second of an inch. Thisresult is accomplished by mounting rotary collars or disks B, Figs. 5 and 7, on the opposite ends of the metal core or body of the roll where they rest on stationary steps or shelves 35 on the apron bars 9 and thus positively limit the movement of the roll toward the apron bar. Normally these disks do not revolve with the roll, but the gudgeons at the opposite ends of the roll body revolve in them. These disks can roll slightly backward and forward on the steps 35 to accommodate the passage of lumps between the roll and the apron, but the roll is normally held by the weighting mechanism with its solid ends pressed firmly against the apron.

With the foregoing construction the mounting of the top rolls 6, as above described, and the elastic nature of the relatively thick covers R on them, cooperate to provide a soft elastic grip of the control mechanism on the sliver. This grip is so limited as to permit theslip through the grist or body of fibers held between each middle top roll and its cooperating apron of those fibers, the forward ends of which are firmly exerting a delaying or retarding action on those Because the apron usually is "about one' 6 fibers not so gripped. This action closely resembles the control which a hand spinner applies with her thumb and forefinger as she allows a roving to slip slowly through her hand to the spindle while she revolves the spinning wheel. She governs the degree of draft in this way.

Referring to Fig. 6 it will be seen that the sliver meets the roll at the point T and is held against the roll up to the point T where it passes out of contact with it. Consequently, long fibers in the grip of the delivery rolls, and which extend back through the control mechanism perhaps for three or four inches, and often more, can be pulled through the body of fibers held in the corn trol region T to T, but the force required to do so is much greater than would be required if this path were straight.

This mechanism will operate on the entire range of fibers used in the textile industry, whether they consist of cotton, wool, rayon, vegetable or synthetics, or mixtures of such fibers, and whether the staple is short, or is the longest wool. With short fibers, such as cotton, a considerable proportion will not reach from the delivery rolls into the grist held under pressure in the control mechanism, so that the latter does not act on the tail ends of these shorter fibers while their forward ends are being pulled through by the delivery rolls, but these fiber tail ends are restrained by other fibers on which this control mechanism does act while they are being pulled forward .by the front rolls so that a substantial degree of control over the shorter fibers is exerted by this mechanism.

In using the machine the spacing of the control mechanism from the front rolls is never changed, but the rear rolls customarily are spaced from the front rolls by a distance slightly greater than the maximum fiber length of the sliver being operated upon. The extreme spacing, as above indicated, may vary from a minimum of about three inches to a maximum of nine inches, or more.

The control mechanism should be positioned as close to the front rolls as is practical for smooth running, cleaning, accommodation of a trumpet, and similar considerations.

The relation of the speeds at which the bottom rolls 2 and 4 are driven will be selected to produce the desired draft, and that can be from a very low value, such as five or six, to extremely high values, say fifty, or even more. It is intended that the relative speeds of the rolls 3 and 4 will be standardized at a low. ratio, such as between 1 to 1.10 and 1 to 1.60, and that the only roll speed which will be adjusted is that of the back bottom roll 4 which will be changed by a suitable adjustment of the overall-draft-change gear. Preferably the rolls 3 and 4 are geared directly together so that their ratio remains unchanged by the adjustment of the speed of the latter. The front and rear rolls can be geared together through a change gear mechanism so that the rear roll will be driven from the front roll and the speed relationship between them can be adjusted in accordance with the desired draft. As above stated, the speed of the middle bottom roll 3 which drives the apron, and from which the middle top roll is driven, is made only sufficient to maintain the length of the sliver between the holding rolls 4 and I and the middle rolls taut. It is not intended that there shall be any draft in this region, but it is desirable to take up the stretch in this section. of the slivers-This is particularly true when wool or other naturally curly fibers are present in the composition of the sliver.

While the main advantages of drafting mechanisms embodying this invention, as compared to the prior art constructions, are the extraordinary range of staple lengths which it will handle while still producing an exceptionally uniform product, together with its simplicity and the elimination of many adjustments for different staple lengths, a further important advantage is the fact that drawing mechanisms made in accordance with this invention occupy only about half the width of the orthodox systems. in a mill. With this invention remarkable uniformity in the character of the final sliver produced has been achieved, and the quality of the sliver in other respects, particularly in the parallelization of the fibers, is superior to that produced by the orthodox drafting methods and mechanisms.

It will also be understood that while the invention has been herein shown and described as embodied in a drafting mechanism of the type used in spinning and roving frames, it is equally applicable to all types of drafting mechanisms. In drawing frames the rolls of course are much longer and the middle top roll, instead of being frictionally driven at its ends may be geared directly to the middle bottom roll corresponding to the roll 3 so that its drive is positive, this being accomplished through gears G as shown in Fig. 4a. Thus, the invention may be embodied in a considerable variety of other forms within the spirit and scope thereof.

The strands being drafted have generally been referred to above as slivers, that term being used in a generic sense to include any material capable of being drafted in a mechanism of the character here disclosed.

The expressions different effective diameters and lesser effective diameter have to do with the provision of, and are intended to define, an upper middle roll with a central portion of lesser actual diameter (see Fig. '7 or witha resilient central portion of the same (see Figs. 1, 2 and 5), or lesser actual diameter (see Fig. 7), or by a lower middle roll with a central portion of lesser diameter (see' Fig. 7, and specification column 5,

lines -26) or a combination thereof, which provide between the central portions of the middle rolls a light frictional grip of the fibres, either because of lesser actual diameter of one or more of said central portions or because of the resilient character thereof which in operation provides a lesser effective diameter than the end portions due to the localized pressure of the sliver, the sliver, of course, in all cases being between the apron and the central portion of said upper roll.

Having thus described my invention, what I desire to claim as new is:

1. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the average fiber length of the sliver to feed and draft it, mechanism for revolving said roll-s at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying sliversupporting apron, a lower apron driving roll within said apron, an upper roll in contact with This space is valuable said apron and mounted above said driving roll and said apron, one of said rolls having diiferent effective diameters, the outer peripheral end portions of said roll having a diameter sufficient to provide firm pressure contact of said end portions with said apron, the central portion of said roll having a smooth peripheral surface and being of lesser effective diameter to provide between the central portions of said roll and its opposing roll a light frictional grip on the fibers of the sliver being drafted between said apron and said upper roll.

2. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater thanthe average fiber length of the sliver to feed and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying sliversupporting apron, a lower apron driving roll within said apron, an upper roll in contact with said apron and mounted above said driving roll and said apron, said upper roll having different effective diameters, the outer peripheral end portions of said roll having a diameter sufficient to provide firm pressure contact of said end portions with said apron, the central portion of said roll having a smooth peripheral surface and being of lesser effective diameter to provide a light frictional grip on the fibers of the sliver being drafted between said apron and said upper roll.

3. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the average fiber length of the sliver to feed and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying sliversupporting apron, a lower apron driving roll within said apron, an upper roll in contact with said apron and mounted above said driving roll and said apron, said upper roll having different effective diameters, the outer peripheral end portions of said roll having a diameter suflicient to provide firm pressure contact of said end portions with said apron, the central portion of said roll having a smooth peripheral surface and being of lesser actual diameter to provide a light frictional grip on the fibers of the sliver being drafted between said apron and said upper roll.

4. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the average fiber length of the sliver to feed and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a nism comprising an endless underlying sliversupporting apron, a lower apron driving roll within said apron, an upper roll in contact with said apron and mounted above. said driving roll and said apron, said lower roll having different effective diameters, the outer peripheral end portions of said roll having a diameter sufficient to provide firm pressure contact of said end portions with said apron, the central portion of said roll having a smooth peripheral surface and being of lesser effective diameter to provide a light frictional grip on the fibers of the sliver being drafted between said apron and said upper roll.

5. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the average fiber length of the sliver to feed and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying s1iversupporting apron, a lower apron driving roll within said apron, an upper roll in contact with said apron and mounted above said driving roll and said apron, said lower roll having different effective diameters, the outer peripheral end portions of said roll having a diameter suificient to provide firm pressure contact of said end portions with said apron, the central portion of said roll having a smooth peripheral surface and being of lesser actual diameter to provide a light frictional grip on the fibers of the sliver being drafted between said apron and said upper roll.

6. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the average fiber length of the sliver to feed and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said-pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying sliversupporting apron, a lower apron driving roll within said apron, an upper roll in contact with said apron and mounted above said driving roll and said apron, said upper roll having different effective diameters, the outer peripheral end portions of said roll having a diameter sufficient to provide firm pressure contact of said end portions with said apron, the central portion of said roll having a resilient smooth peripheral surface and being of lesser effective diameter to provide a light frictional grip on the fibers of the sliver being drafted between said apron and said upper roll.

7. The drafting mechanism as claimed in claim 6 wherein said lower roll is provided with a central portion of lesser actual diameter than the diameter of the end portions thereof.

8. The drafting mechanism as claimed in claim 1 further including an apron bar and means mounted adjacent the apron bar positively limiting bodily movement of said upper roll toward said apron bar.

9. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the average fiber length of the sliver to feed. and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying sliver supporting apron, a lower apron drivin roll within said apron, an upper roll in contact with said apron and mounted above said driving roll and said apron, said upper roll having outer peripheral end portions and a central portion, said end portions each having a diameter at least as great as that of said central portion and being constructed to provide firm pressure contact with said apron, said central portion having a smooth peripheral surface and being constructed to provide a light frictional grip on the fibers of the sliver being drafted between said apron and said upper roll.

10. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the average fiber length of the sliver to feed and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying sliver supporting apron, a lower apron driving roll within said apron, an upper roll in contact with said apron and mounted above said driving roll and said apron, said upper roll having outer peripheral end portions and a central portion, said end por- 'tions each having a diameter at least a great as that of said central portion and being constructed to provide firm pressure contact with said apron, said central portion having a clearance providing a recess and together with said apron being constructed and arranged to provide so limited a grip on the body of fibers of a sliver being drafted between said apron and said upper roll as to permit slip of fibers therefrom.

11. A drafting mechanism of the character described having a drafting zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the aver age fiber length of the sliver to feed and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying sliver supporting apron, a lower apron driving roll within said apron, an upper roll in contact with said apron and mounted above said driving roll and said apron, said upper roll having outer peripheral end portions and a central portion, said end portions each having a greater diameter than that of said central portion to provide firm pressure contact with said apron, said central portion having a smooth peripheral surface to provide a light frictional grip on the fibers of the sliver being drafted between said apron and said upper roll.

12. The drafting mechanism as claimed in claim 10 further including an apron bar and means mounted adjacent the apron bar positively limiting bodily movement of said upper roll toward said apron bar.

13. A drafting mechanism of the character described having a zone comprising a pair of delivery rolls at one end and a pair of holding rolls at its opposite end, means supporting said rolls to act simultaneously on portions of a sliver spaced apart by a distance greater than the average fiber length of the sliver to feed and draft it, mechanism for revolving said rolls at the speeds necessary to produce the desired draft, and a rotary fiber control mechanism mounted between said pairs of rolls and through which said sliver is drawn by said delivery rolls, said control mechanism comprising an endless underlying sliver supporting apron, an apron bar within said apron, a lower apron driving roll within said apron, an upper roll in contact with said apron and mounted above and forwardly of said driving roll and above said apron, said upper roll having outer peripheral apron-contacting end portions and a central portion therebetween, said end portions each having a diameter at least as great as that of said central portion and being constructed and mounted with said apron-contacting end portions pressed downwardly against said apron, said central portion having a clearance providing a recess and together with said apron being constructed and arranged to provide so limited a grip on the body of fibers of a sliver being drafted between said apron and said upper roll as to permit slip of fibers therefrom, said drafting mechanism including means positively limiting bodily movement of said upper roll towards said apron bar to provide therebetween radially opposite said apron-contacting end portions suflicient space for said apron plus a clearance.

14. The drafting mechanism as claimed in claim 13 further including gearing connecting said lower apron driving roll and said upper roll to positively drive said upper roll.

BENJAMIN C. SHAW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date.

1,827,385 Cornibert Oct. 13, 1931 2,074,556 Pilz Mar. 23, 1937 2,233,963 Shaw Mar. 4, 1941 2,255,821 Schlipp et a1 Sept. 16, 1941 2,329,655 Shaw Sept. 14, 1943 2,471,056 Bird May 24, 1949 2,471,057 Bird May 24, 1949 

